From Vitamins to Solar

By Stephen Luntz

It is not an obvious path from Prof Andrew Holmes’ PhD on the synthesis of vitamin B12 to the next generation of solar cells, but it has now led him back to the University of Melbourne where he completed his undergraduate degree.

Holmes’ doctorate was at University College London, where Franz Sondheimer was making large molecules called annulenes. He then joined Albert Eschenmoser in Zurich. “B12 was the most complex naturally occurring small molecule (i.e. not a protein) known at the time, so it was a sort of Everest,” he says.

The work won him a lectureship at Cambridge, where he became a polymer chemist after his group played a key role in developing light-emitting polymers (LEPs) – the 1989 discovery that certain semiconducting plastics emit light when electricity is applied. Holmes then became Director of the Melville Laboratory of Polymer Synthesis.

LEPs may soon replace the liquid crystal displays (LCDs) used in laptops and TVs. Inkjet printing allows the creation of full colour flat screens of varying sizes, without the requirement for them to be backlit. These displays can be thinner and lighter than LCDs, and may also be cheaper.

The original polymers had short life-spans and inadequate efficiency, but all these problems have been overcome in a commercial environment. The work won the project team the 2003 Descartes Prize, which is one of Europe’s most valuable scientific prizes.

In 2012 Holmes was awarded a Royal Medal, in part for this work. “It’s exciting to work in polymer chemistry, an area that can lead to a diverse range of applications from the development of more energy-

efficient products to the greater understanding of biological processes,” he said at the time. By that stage he had been lured home by an ARC Federation Fellowship.

Much of Holmes’ work has been on biologically active chemicals. However, his current role heading the Victorian Organic Solar Cells Consortium (VICOSC) turns the concept of light-emitting polymers on its head – converting light into electricity. In May VICOSC won headlines announcing the capacity to print organic photovoltaic cells onto A3-sized sheets – ten times their previous maximum size.

“Silicon is dominant in the marketplace,” says Holmes. “It works very well where there is lots of sunshine. However, there is demand for thinner, lighter and more flexible devices. There are a number of technologies that can deliver, but not many of them are able to be put on flexible substrates. In our case we can print layers of material onto plastic.”

The technology would allow printing of solar collectors onto curved or lumpy surfaces such as roofs or the backs of laptop computers. The efficiency is currently much lower than for silicon solar cells, and the dramatic fall in prices of conventional photovoltaics makes it hard for organics to compete on price.

Nevertheless Holmes is optimistic, noting there have been more than 40 years of silicon photovoltaic research but only 10–15 years on organic polymers, of which 6–7 years have been “serious”. “Ultimately we may produce something that is at least comparable with silicon,” he says. Organic cells experience a smaller drop in efficiency under cloud or shade than silicon-based panels, and Holmes thinks there may be a niche in covering the sides of buildings that face away from direct sunlight if the cost can be reduced enough.

VICOSC is far from alone in pursuing the dream of organic sources of solar power, but Holmes says: “We have one advantage in that we have built a team spanning benchtop to rooftop”. Besides the universities of Melbourne and Monash, and CSIRO, VICOSC includes Bluescope Steel, Bosch SEA and film manufacturer Innovia, which produces polymer bank notes.

Holmes adds that the polymers have outperformed the industry rule-of-thumb in scaling up from postage stamp-sized test cells. “To compete with silicon on a large scale we might need to achieve 16% [efficiency] in the lab. We’re currently approaching 10%,” he says.

As Foreign Secretary of the Australian Academy of Science, Holmes provides opportunities for young Australian researchers to “have a voice on the international stage and show their wares,” for example by enabling 10–15 early-stage researchers to attend an annual gathering addressed by Nobel Prize winners. “Australia has 0.3% of the world’s population and produces about 3% of the science but we need to gain access to the other 97% if we are to progress,” he says.

Holmes’ father was a research chemist, but he says: “Nearly everyone who has had a great opportunity in science can look back on school teachers who inspired them”. His desire to go to Cambridge was cemented by reading James Watson’s account of discovering the structure of DNA, although when he got there he discovered “there was a lot less tennis”.

It is not an obvious path from Prof Andrew Holmes’ PhD on the synthesis of vitamin B12 to the next generation of solar cells, but it has now led him back to the University of Melbourne where he completed his undergraduate degree.